DE-78 10 362 discloses a tension spring for transmitting force between a garage wall and the associated garage door. The tension spring is disposed in a protective sleeve in order to minimize the risk of injury to persons and of damage to objects in the event the tension spring breaks. The protective sleeve includes a first pipe overlapping a second pipe, and is directly fastened on the tension spring proper. In the event the tension spring breaks at the center region thereof, the protective sleeve, because of its longitudinal displaceability, expands to a length greater than the length of the tension spring and effects an axial guidance of the breaking tension spring as a result of the mutual overlapping of the first and second pipes. However, if the tension spring breaks at its end regions, the shown protective sleeve can no longer function to effect an axial guidance of the breaking tension spring. Thus, in the event of the above, the tension spring is laterally deflected in an uncontrollable manner, and is likely to cause injury to persons or damage to property in spite of the presence of the protective sleeve.